Aromatic halogenation, the replacement of a hydrogen atom by one of the group VIIa elements, is an important tool in organic chemistry for converting aromatic compounds into specific compounds through electrophilic aromatic substitution. This process contrasts from the substitution of alkyl compounds through nucleophilic substitution in that in aromatic halogenation the process generally occurs via a two step addition-elimination mechanism in which the pi electrons of the aromatic ring attack the electrophilic reagent forming a cationic intermediate, or Meisenheimer complex, which then eliminates a leaving group, the hydrogen, to form the desired substituted product. This process is typically carried out through the reaction of Cl2, Br2, or I2 with a catalyst to mediate the reaction. Elemental iodine is the easiest, safest and greenest to work with as bromine is volatile and can cause severe burns to the eyes and skin and cholrine has a bp at -34 degrees C. When Chlorine is in gas form, which it is at room temperature, it can cause severe respiratory irritation, damage and even death. In this lab the halogenation of the aromatic compound will be carried out through iodination. The iodination reaction this lab uses also allows for the reaction to be efficient and selective, which should lead to good yields of monoiodinated product, and the more environmentally benign reaction uses a less hazardous oxidizing agent (NaOCl, household bleach) and a relatively benign solvent, ethano, thereby creating less toxic wastes.
Some of this is paraphrased from the Intro to the lab procedure. Did you cut and paste or paraphrase that report? You need to cite them if you are going to use their words or ideas.
Graphic example of aromatic halogenation, specifically, iodination.
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iodine.jpg
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This figure needs a citation.
Procedure:
The procedure came from Doxsee, K. M.; Hutchison, J. E. Green Organic Chemistry - Strategies, Tools, and Laboratory Experiments, Print 2004; pp 186-187. Step number 7. and Gilbertson, R.; Parent, K. E.; McKenzie, L. C.; Hutchison, J. E. Electrophilic Aromatic Iodination of 4'-Hydroxyacetophenone Greener Approaches to Undergraduate Chemistry Experiments, Print Kirchhoff, M., Ryan, M., Eds.; American Chemical Society: Washington D.C., 2002; pp 1-3.
Adaptations included the use of vanillin instead of 4' Hydroxyacetophenone
Data:
Initial measurements for the reaction:
In a 100ml round-bottom flask containing a magnetic stir bar, add 1.01 g of vanillin (White or very slightly yellow needles) in 20 ml of ethanol
Add 1.20 g of sodium iodide sig figs. (cream color, powdery) then cool down with an ice/water bath.
With the use of a separatory funnel 11 ml Sodium hypochlorite solution 6%w/w (bleach) was added, drop-wise for 10 min . The solution changed color from pale yellow to red-brownish.
1.jpg
Warmed up at room temperature, which was 22.5 Celsius and was stir it for 10min typo?
Workup and Isolation:
After Adding 10 ml of sodium thiosulfate solution (10% w/w) the Ph was 8 , then acidify with 4.5 ml of Hydrochloric acid (10% w/w) getting a Ph of 2 (turning yellowish). subject/verb agreement.
Remove the ethanol from suspension on rotary evaporator, for less than 10 minute
2.jpg
The flask cooled for 10 minutes
Proceed to vacuum filtration for about 8 minute. The weight of the crude product was 2.89 g
3.jpg
The crude product was place in a 125ml Erlenmeyer flask and heated. 25 ml of 2-propanol was added to generate a clear solution. After allowed the solution to cool and and proceed with vacuum filtration, a minimum amount of crystals was collected,
How much is "minimal?" Please explain. What did they look like? Did you get a melting point?
Conclusion:
The incorporation of iodine via the iodination of Vanillin produced variable resutls. An analysis of the melting point and final product mass data suggests the volume of solvent used altered the recystallization of the experiment. Where is the melting point data? Adding too much solvent can cause the loss of the more soluble compound in a solution, resulting in a lack of crystal formation and a altered molecular characteristics of the final product. Remember, recystalization begins with the addition of a solvent to dissolve an impure solid, 2-propanol was used as the solvent in this experiment. However, due to the 20+ml of 2-propanol used, very few solid crystals formed during the ice bath. You seem quite confident that this is the source of the problem. I would like to hear you explain why you think so. The lack of crystals formed accounted for the loss of product mass compared with the original reagents added. In addition the extra propanol used could have changed the molecular qualities of the product through dilution. Thus, accounting for the difference between the experimental melting point of 151.8 C melting points are always reported as temperature ranges. and the reported melting point of 183-185 C. The expected final product shoud have been Iodovanillin, however the differing experimental melting point showed the product did not match this molecular compound. Suggestions for repeating this experiment include allowing the solution to heat slowly as the solvent is added during the recrystallization process. Next, do not over swirl the mixture while adding the solvent. Once the solution has been gently stirred allow the flask to sit undisturbed before adding more solvent. This technique will allow for any cloudiness caused by turbidity to settle. Continued stirring while adding the solvent could have delayed the observation that the solution cloudiness was clearing.
Post-Lab Q this week’s Elimination lab: Calculate the atom economy for this reaction. Atom economy is defined on Wikipedia, but essentially is the mass of the desired product divided by the mass of all reactants (don’t include catalysts or solvents in our reaction).
Vanillin (C8H803) has a molecular weight of 152.15g /mol and Iodovanillin (C8H7IO3) is 278.04g/mol. The % atom economy for Iodovanillin is 278.04g/278.04g+152.15g =.6463190683 or 64.632%
calculation is incorrect.
This report earned the following scores: format (2/2) style (0.5/2) data (1.5/3) quality of result (0.5/1) quality of reported data (0.5/1) conclusion (1/2) error (1/1) post-lab Q (0.5/2) for a total of 7.5/14. LOTS of room for improvement. The report gives the impression that it was done in a hurry, and without much editing. You are all responsible together for peer reviewing the report, and the effort will pay off for everyone.
Iodination of Vanillin
sol will rewrite: Introduction:
Aromatic halogenation, the replacement of a hydrogen atom by one of the group VIIa elements, is an important tool in organic chemistry for converting aromatic compounds into specific compounds through electrophilic aromatic substitution. This process contrasts from the substitution of alkyl compounds through nucleophilic substitution in that in aromatic halogenation the process generally occurs via a two step addition-elimination mechanism in which the pi electrons of the aromatic ring attack the electrophilic reagent forming a cationic intermediate, or Meisenheimer complex, which then eliminates a leaving group, the hydrogen, to form the desired substituted product. This process is typically carried out through the reaction of Cl2, Br2, or I2 with a catalyst to mediate the reaction. Elemental iodine is the easiest, safest and greenest to work with as bromine is volatile and can cause severe burns to the eyes and skin and cholrine has a bp at -34 degrees C. When Chlorine is in gas form, which it is at room temperature, it can cause severe respiratory irritation, damage and even death. In this lab the halogenation of the aromatic compound will be carried out through iodination. The iodination reaction this lab uses also allows for the reaction to be efficient and selective, which should lead to good yields of monoiodinated product, and the more environmentally benign reaction uses a less hazardous oxidizing agent (NaOCl, household bleach) and a relatively benign solvent, ethano, thereby creating less toxic wastes.
Some of this is paraphrased from the Intro to the lab procedure. Did you cut and paste or paraphrase that report? You need to cite them if you are going to use their words or ideas.Graphic example of aromatic halogenation, specifically, iodination.
||
Procedure:
The procedure came from Doxsee, K. M.; Hutchison, J. E. Green Organic Chemistry - Strategies, Tools, and Laboratory Experiments, Print 2004; pp 186-187. Step number 7. and Gilbertson, R.; Parent, K. E.; McKenzie, L. C.; Hutchison, J. E. Electrophilic Aromatic Iodination of 4'-Hydroxyacetophenone Greener Approaches to Undergraduate Chemistry Experiments, Print Kirchhoff, M., Ryan, M., Eds.; American Chemical Society: Washington D.C., 2002; pp 1-3.
Adaptations included the use of vanillin instead of 4' HydroxyacetophenoneData:
Initial measurements for the reaction:
In a 100ml round-bottom flask containing a magnetic stir bar, add 1.01 g of vanillin (White or very slightly yellow needles) in 20 ml of ethanol
Add 1.20 g of sodium iodide sig figs. (cream color, powdery) then cool down with an ice/water bath.
With the use of a separatory funnel 11 ml Sodium hypochlorite solution 6%w/w (bleach) was added, drop-wise for 10 min . The solution changed color from pale yellow to red-brownish.
Warmed up at room temperature, which was 22.5 Celsius and was stir it for 10min typo?
Workup and Isolation:
After Adding 10 ml of sodium thiosulfate solution (10% w/w) the Ph was 8 , then acidify with 4.5 ml of Hydrochloric acid (10% w/w) getting a Ph of 2 (turning yellowish). subject/verb agreement.
Remove the ethanol from suspension on rotary evaporator, for less than 10 minute
The flask cooled for 10 minutes
Proceed to vacuum filtration for about 8 minute. The weight of the crude product was 2.89 g
The crude product was place in a 125ml Erlenmeyer flask and heated. 25 ml of 2-propanol was added to generate a clear solution. After allowed the solution to cool and and proceed with vacuum filtration, a minimum amount of crystals was collected,
How much is "minimal?" Please explain. What did they look like? Did you get a melting point?Conclusion:
The incorporation of iodine via the iodination of Vanillin produced variable resutls. An analysis of the melting point and final product mass data suggests the volume of solvent used altered the recystallization of the experiment. Where is the melting point data? Adding too much solvent can cause the loss of the more soluble compound in a solution, resulting in a lack of crystal formation and a altered molecular characteristics of the final product. Remember, recystalization begins with the addition of a solvent to dissolve an impure solid, 2-propanol was used as the solvent in this experiment. However, due to the 20+ml of 2-propanol used, very few solid crystals formed during the ice bath. You seem quite confident that this is the source of the problem. I would like to hear you explain why you think so. The lack of crystals formed accounted for the loss of product mass compared with the original reagents added. In addition the extra propanol used could have changed the molecular qualities of the product through dilution. Thus, accounting for the difference between the experimental melting point of 151.8 C melting points are always reported as temperature ranges. and the reported melting point of 183-185 C. The expected final product shoud have been Iodovanillin, however the differing experimental melting point showed the product did not match this molecular compound. Suggestions for repeating this experiment include allowing the solution to heat slowly as the solvent is added during the recrystallization process. Next, do not over swirl the mixture while adding the solvent. Once the solution has been gently stirred allow the flask to sit undisturbed before adding more solvent. This technique will allow for any cloudiness caused by turbidity to settle. Continued stirring while adding the solvent could have delayed the observation that the solution cloudiness was clearing.
Post-Lab Q this week’s Elimination lab:Calculate the atom economy for this reaction. Atom economy is defined on Wikipedia, but essentially is the mass of the desired product divided by the mass of all reactants (don’t include catalysts or solvents in our reaction).
Vanillin (C8H803) has a molecular weight of 152.15g /mol and Iodovanillin (C8H7IO3) is 278.04g/mol. The % atom economy for Iodovanillin is 278.04g/278.04g+152.15g =.6463190683 or 64.632%
calculation is incorrect.
This report earned the following scores: format (2/2) style (0.5/2) data (1.5/3) quality of result (0.5/1) quality of reported data (0.5/1) conclusion (1/2) error (1/1) post-lab Q (0.5/2) for a total of 7.5/14. LOTS of room for improvement. The report gives the impression that it was done in a hurry, and without much editing. You are all responsible together for peer reviewing the report, and the effort will pay off for everyone.